Citrus exocortis is caused by

Options

A. Mycophage
B. Viroids
C. Prions
D. Cyanophages

Answer

**Step-by-Step Solution:**

1. **Understanding the Disease**: Citrus exocortis is a disease that affects citrus plants. It is important to identify the causative agent of this disease.

2. **Identifying the Causative Agent**: The causative agent of Citrus exocortis is known to be viroids. Viroids are unique infectious agents that are distinct from viruses.

3. **Characteristics of Viroids**: Viroids are characterized by being the smallest infectious pathogens. They consist solely of single-stranded RNA and lack a protein coat, which differentiates them from typical viruses.

4. **Effects of Citrus Exocortis**: The disease caused by viroids leads to stunted growth in citrus plants and a reduction in their yield. This highlights the economic impact of the disease on citrus agriculture.

5. **Eliminating Incorrect Options**:
- Mycophages are viruses that specifically infect fungi, so they are not related to citrus plants.
- Prions are infectious agents composed of protein that cause diseases, but they do not cause Citrus exocortis.
- Cyanophages are viruses that infect cyanobacteria, which is also unrelated to citrus plants.

6. **Conclusion**: Based on the information provided, the correct answer to the question "Citrus exocortis is caused by?" is viroids.

**Final Answer**: Citrus exocortis is caused by viroids.

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